1. Technical Field of the Invention
The present invention relates to a fixing device for fixing a toner image transferred on a recording material, and more particularly, to a fixing device which is provided with a pair of fixing rollers which rotate in pressing contact with each other and a mold releasing agent supply means for feeding a mold releasing agent to the fixing rollers.
2. Description of Related Art
In a conventional fixing device, it has heretofore been arranged to apply a mold releasing agent onto the surface of fixing rollers in order to prevent toner from being offset to the fixing rollers, and various proposals have been raised to regulate the amount of mold releasing agent to be applied.
For instance, U.S. Pat. No. 4,045,165 discloses a fixing device wherein a supply roller for feeding a mold releasing agent to a fixing roller is provided to be movable toward and away from the fixing roller to prevent excessive supply of the mold releasing agent. In the U.S. Pat. No. 4,285,295, there is disclosed a fixing device wherein a mold releasing agent supply roller is fixedly disposed relative to a fixing roller with the same purpose as mentioned above, and a mold releasing agent supply pad is provided to be movable toward and away from the supply roller.
In such fixing devices, however, when a toner image is fixed onto a transparent film made of resin (hereinafter called as OHP film) which is used as an original for overhead projectors, the mold releasing agent tends to be somewhat excessively remained on the surface of the fixing roller after the toner image is fixed onto the OHP film which causes to lower the quality of an image formed on the OHP film. Especially, when an image formed on the OHP film is reproduced by a light transmissible colored toner, the reproducibility of the image is remarkably lowered. Further, it was also found by the inventor of the present invention that the OHP sheet often slipped by the mold releasing agent coated on the surface of the fixing rollers and is not properly taken into nip section of the fixing rollers.
In the device disclosed in the above-mentioned U.S. Pat. No. 4,285,295, there is a problem that foreign substance such as toner and paper dust particles sometimes adhere to the portion of the supply pad where it is brought in contact with the supply roller, and the particles collected in the portion of the supply pad prevents the mold releasing agent from being uniformly supplied on the surface of the supply roller and therefore causing continuous lines on the surface of the supply roller in the direction of circumference thereof by scraping off some of the mold releasing agent.